Method of preventing formation of boiler scale



NOV. 8, 1966 5, V N 3,284,32g

METHOD OF PREVENTING FORMATION OF BOILER SCALE Filed April 9, 1964 IN V EN TOR. ID rd E) L EV! :4 E.

A TOQ MEY United States Patent O 3,284,328 METHOD OF PREVENTING FORMATION OF BOILER SCALE Sidney Levine, 8404 Donneybrook Drive, Chevy Chase, Md. Filed Apr. 9, 1964, Ser. No. 359,553 2 Claims. (Cl. 204149) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to the field of boiler scale inhibitors and is a continuation-in-part of my copending application Serial Number 231,875, filed October 19, 1962, now abandoned.

Boiler scale is likely to form on the internal areas of any boiler or tank in which water is evaporated. This scale which usually comprises deposits of adherent inorganic sulfates, carbonates and other inorganic salts from the water will in time interfere with the efiiciency of the boiler or tank. Present methods of dealing with the problem generally utilize cleaning procedures rather than preventative measures. I

It has been proposed to use electrical currents in various ways to protect against boiler scale. No investigator, however, has suggested the principle which underlies the present invention which comprises the applying of a direct current to the water in the boiler by means of anodes and cathodes made of chemically inert and insoluble material suspended within the boiler and electrically insulated from the walls thereof while heat is being supplied to the boiler or evaporator.

Accordingly, an object of this invention is to provide an improved method and apparatus for inhibiting the formation of scale on the walls of a boiler or evaporator tank.

Another object of the invention is to provide an im I proved method and apparatus for inhibiting the formation of boiler scale utilizing chemically inert and insoluble electrodes and a direct current applied thereto. That is to say, electrodes which are considered to be inert or electrolytically insoluble in the electro-chemical art such as platinum and carbon electrodes.

The prior art teaches the application of both alternating and direct current to boilers or evaporators for diverse purposes and with varying results. None of the prior teachings, however, recognize the unobvious, but critical, requirement of this invention which is that the current must be applied throughout the evaporating or heating cycle. Tests run by the inventor show that it is not enough to merely treat the water and subsequently use it in a boiler or evaporator without the electrodes and their applied direct current.

The drawing shows a simplified, sectional view of a boiler protected by the present invention.

Both the method and apparatus of the present invention will be described with reference to the figure. The boiler or tank 1 to be protected has a well 2 in its bottom and is normally filled with water to level 3. Chemically inert and insoluble electrodes 4 and 5, mounted on insulating hangers 6 and 7 respectively which insulate the electrodes from the wall of tank 1, are suspended within the water. Electrodes 4 and are connected through conductors within the insulating hangers to a source of direct current Patented Nov. 8, 1966 8 so that electrode 4 is the cathode and electrode 5 the anode. Means, not shown, should be provided for removing the cathode periodically for cleaning or replacement and means, not shown, should also be provided in well 2 for drawing oti material which falls from the cathode.

In operation a direct current voltage is applied to the electrodes when the boiler or evaporator is in operation beginning when boiler water is at ambient temperature and continuing until boiler is shut down and water temperature returns to ambient. The walls of the boiler or tank remain substantially free of boiler scale while an insoluble deposit occurs on the cathode. Some of the material falls from the electrode into well 2. It is nonadherent and can be drawn off the bottom.

It should be stated at this point that the insoluble deposit which collects on the cathode and/ or settles out in well 2 does not appear to appreciably affect the hardness of the water and as evaporation progresses and additional untreated tap water is added from time to time and subsequently evaporated, the hardness rises. Hardness tests performed during the evaporation indicated harder water as the test progressed. The material which plated out on the cathode 4 or settled in well 2 did not appear to appreciably lower the hardness of the water. In the process taught by this invention water is not purified or rendered solute free.

The present invention is advantageous in that it is less expensive to use than water softeners or ion exchangers or cleaning. It also permits a wider selection of waters that can be used for boiler operation.

I claim:

1. The method of removing carbonates and other scale producing salts from water in an evaporator comprising:

immersing in the water of said evaporator at least one anode and one cathode which are chemically inert and electrolytically insoluble,

electrically isolating and spacing said anode and cathode from the inner walls of said evaporator,

heating to boiling the water in said evaporator, and

applying direct current potential to said anode and cathode prior to said heating, during said heating and continuing until the water has returned to ambient temperature after the termination of said heating.

2. The method of claim 1 including the steps of:

removing, cleaning and replacing said cathode periodically.

References Cited by the Examiner UNITED STATES PATENTS 478,048 6/ 1892 Collins 204-149 1,051,182 1/1913 Ackerman 204149 1,843,673 2/ 1932 Hessenbruch 204149 3,081,241 3/1963 Smith 204149 3,198,724 8/1965 Cross et a1 204274 FOREIGN PATENTS 181,018 5/ 1922 Great Britain.

JOHN H, MACK, Primary Examiner.

WINSTON A. DOUGLAS, ALLEN B. CURTIS,

Examiners. T. TUNG, Assistant Examiner. 

1. THE METHOD OF REMOVING CARBONATES AND OTHER SCALE PRODUCING SALTS FROM WATER IN AN EVAPORATOR COMPRISING: IMMERSING IN THE WATER OF SAID EVAPORATOR AT LEAST ONE ANODE AND ONE CATHODE WHICH ARE CHEMICALLY INERT AND ELECTROLYTICALLY INSOLUBLE, ELECTRICALLY ISOLATING AND SPACING SAID ANODE AND CATHODE FROM THE INNER WALLS OF SAID EVAPORATOR, HEATING TO BOILING THE WATER IN SAID EVAPORATOR, AND APPLYING DIRECT CURRENT POTENTIAL TO SAID ANODE AND CATHODE PRIOR TO SAID HEATING, DURING SAID HEATING AND CONTINUING UNTIL THE WATER HAS RETURNED TO AMBIENT TEMPERATURE AFTER THE TERMINATION OF SAID HEATING. 